A multi-objective decision is a decision that is made based on multiple objectives. As an example, consider selecting which car one would like to purchase. There may be several different criterions that may affect the decision, such as a price of the car, comfort, safety and fuel economy. In a multi-objective problem, there may be several solutions that are all considered Pareto optimal as they are preferable over other Pareto optimal solutions in at least one objective. Referring to the car example and assuming two criterions, a first solution in which the price is 10K USD and safety is 5 may be considered preferable over a second solution in which the price is 12K USD and safety is 5. However, a third solution in which the price is better but the safety criterion is worse, such as price 8K USD and safety 4, is not in itself preferable over the first solution. In order to decide between one may need to define preferences between the different objectives.
Identification of Pareto optima solutions, also referred to as efficient frontier, may be referred to as Multi-Criterion Decision Making (MCDM). The solution of the MCDM may typically be driven by a human Decision-Maker (DM), who may choose a solution from the efficient frontier based upon their personal preferences. Though attempts have been made to formalize the user's preference so as to allow automatic selection of the optimal solution out of the efficient frontier for a specific user, studies have shown that people rarely succeed in formulating their preferences. In addition, the selection is sometimes affected by physiological biases or other factors, which may not necessarily be rationale and may not adhere to a declared preference of the user.